- Spinach – Refrigerate seeds 1 week before sowing to help germination. Not pre-sprouting.
- Onion Seeds – Pre-soak seed in compost tea for an hour to prevent damping off and other fungal diseases.
- Swiss Chard – Soak seeds overnight before sowing to hasten germination.
- Beet Seeds can benefit from a brief soaking in water for 4-6 hours before planting to soften seed coat.
Seeds that benefit from soaking in water:
Some seeds germinate quicker if they are soaked in water or water and a drop of vinegar before they are planted. Seeds with hard coats, big seeds, and seeds with wrinkled coats benefit from soaking in water before planting. Put these seeds in a shallow bowl of water or place them on a damp paper towel and put them in a sealed plastic bag to soak up the moisture. Warm water will reduce the soaking time. Add a few drops of kitchen vinegar to the water; the acid in the vinegar will also help breakdown the seed coat. Soak these seeds just long enough for the seed coats to draw up moisture—about 12 hours or overnight. These seeds include:
- Beet seeds
- Swiss chard seeds
- Lettuce seeds (a lot of info at the link and above) can be one of the most difficult seeds to uniformly germinate due to thermodormancy and photodormancy. Lettuce will not germinate well if temps are too high or if seeds are in the dark.
- Lettuce starting tips from Harvest to Table and Cornell
- Imbibing or soaking the [lettuce] seeds in cool water for 16–24 hours in a well-lit area before planting will increase the germination percentages greatly. Red light has been found to be the best color for encouraging germination, but if you don’t have access to a non-heating red light, sunlight or full-spectrum light is almost as good. In warm conditions, soaking the seeds in the dark can actually decrease their germination rates. And soaking for less than 16 hours has little to no positive effect on germination rates. From the Grownetwork.
- From SESE – If the temperature exceeds 80 degrees F lettuce will often fail to germinate. Lettuce can be planted during late summer or early fall while the days are still hot provided:
- that the seeds are germinated in the refrigerator for 4-6 days.
- Another method is to soak seed in 10% bleach for 2 hours at 40-60 degrees F followed by 4 water rinses. This method enhances both the speed and amount of germination.
- One more method is to keep soil cool with burlap or boards; remove cover promptly after germination to keep grasshoppers and other pests from enjoying the shaded tender sprouts!
Learned about this technique from an article by Pam Dawling as a solution to germinate seeds that require cool soil, and the need to get them started in the hot deep-south Alabama soil. Her web site is here.
- Crops that germinate best at soil temperatures below 80°F (27°C) include:
- parsley, parsnips
- Getting good soil contact is important, so tamp the row well after planting.
- Small seeds that have been soaked tend to clump together, so after draining off as much water as possible, mix them with a dry material like uncooked corn grits, oatmeal or bran, or use coffee grounds or sand.
- To pre-sprout seeds for extended-season growing:
- First, soak them. Then drain off the water which has not been absorbed, and put the seeds in a suitably cool place.
- Rinse twice a day, draining off the water.
- Usually, it’s best to sprout the seed just until you see it has germinated. Seeds with long sprouts are hard to plant without snapping off the shoot. For most crops, 0.2 inch (5 mm) is enough. For lettuce half that length is good, and one day may be time enough.
- Other tips from this article.
- Sowing at night (or at least as late in the evening as you can) will give better emergence because the temperature-sensitive phase of germination can occur while soil temperatures are lower.
- Reduce the chances of soil “capping” or crusting by keeping soil cultivation to a minimum, and watering ahead of planting. If crusting is likely, avoid tamping or rolling the soil hard.
- With carrots the challenge is to keep the soil surface damp until the seedlings emerge. For large-seeded crops (corn, beans) that we hand sow, we water the furrow generously before we plant. If we have a very well-watered furrow, we skip the tamping. Pre-watering ensures that the water is right there at seed level, where it is less likely to dry out.
- At high temperatures, celery and lettuce do better when they receive some light, therefore don’t sow too deeply. Seeds do need oxygen to germinate. Carrots germinate best in a high oxygen concentration.
- Watering after sowing should be shallow and frequent, until the seedlings emerge. Make sure your direct-seeded crops don’t drown in an excess of water that pushes out all the air. After emergence, less frequent but deeper watering will encourage deeper roots, providing better heat tolerance.